COMPLEX RESISTOR COMBINATIONSChapter 20.3

Resistors Combined in Both Parallel and Series

• Most circuits today employ both series and parallel resistor wiring to utilize the advantages of each type.

• Wiring in parallel allows devices to run independently of the others and allows the potential difference to be the same in each device.

• Wiring in series can be used to control the amount of current flowing through a circuit, which can prevent excessive current reaching the device

Solving Complex Circuits• When determining the equivalent resistance for a complex

circuit you must:

1. Simplify the circuit into groups of series and parallel resistors.

2. Find the equivalent resistance for each group or resistors.

3. Find the total equivalent resistance for the whole circuit.

Complex Resistors Circuit• Schematic diagrams for an arrangement of various

electric devices. The equivalent resistance of the circuit is 10 ohms.

Working Backwards• Work backwards to find the current in and potential

difference across a part of a circuit.• This can be done by using Ohm’s Law and the chart

below:

Series Parallel

Current Same as Total Add to find total

Potential Difference Add to find total Same as total

Example Problem

Find the potential difference and current through each of the resistors in the diagram below.

40 V

15 Ω

4 Ω